The present invention relates to the manufacture of elastic belts as supports used inside tires to bear the load in case of a flat. More precisely, it concerns the methods and means of manufacture of supports embodying at their base an appreciably inextensible belt made by means of reinforcing wires of the type used in reinforcing tires.
In the present description, the term xe2x80x9cwirexe2x80x9d very generally designates both monofilaments and multifilaments or assemblies such as cords, cables, plied yarns or alternatively any equivalent type of assembly, whatever the material and the treatment of these wires. They may, for example, be surface treatments, coating or pre-sizing in order to promote adhesion to the associated molding material.
Patent application EP 0,796,747 describes such supports and patent application EP 1,000,728 describes a particular method of manufacture of such supports.
The method described in patent application EP 1,000,728 consists of molding a support in a molding cavity where a flexible circumferential reinforcing belt has been previously arranged. That belt is thus integrated with the molding material and is intended to bestow certain mechanical properties to the support formed. The device described in document EP 1,000,728 comprises a molding cavity placed around a roughly cylindrical core, the circumference of which can vary between a molding configuration where the diameter of the core matches the reference diameter of the support and a reduced configuration (of so-called mold stripping) where the circumference is less than the product of the reference diameter and the number xcfx80. The principal stages of manufacture are as follows:
a belt (prefabricated in any appropriate manner), containing the reinforcing wires, is deposited around the core in its reduced configuration (mold stripping configuration),
the core molding configuration (reference diameter) is established,
the mold is closed,
the mold is filled under pressure (by injection or transfer),
the mold is opened,
the molded support is extracted.
This known method includes several stages, which constitute a relatively long manufacturing cycle. The time necessary for filling of the mold and reticulation of the molded material is variable, depending mainly on the material used for molding, the different regulating temperatures and the general dimensions of the support, but especially on the local thicknesses of the different parts of the support. In particular, the time necessary for sufficient reticulation of the molded material (for a resistance compatible with the mold stripping and handling stresses), represents a large and irreducible portion of the cycle time. For example, in the case of a support made of rubber, its reticulation takes several minutes. Another large portion of the cycle time corresponds to the operations of molding preparation and removal of the molded support. In fact, placement of the reinforcing belt before the molding operation is difficult, for its proper positioning in relation to the molding cavity has to be assured. Extraction of the support after molding is likewise difficult and requires a considerable effort on the part of the operator, especially in case of large dimensions. Those operations are therefore relatively lengthy and require a consequent immobilization of the production equipment. Furthermore, the mold being naturally open during handling, a considerable heat exchange takes place and tends to cool the mold, which retards the reticulation of the following molding. Likewise, if those operations are carried out manually, this demands an availability of labor at precise moments of the manufacturing cycle in order not to further penalize productivity of the machine with extra waiting time. If placement of the belt in the mold is carried out manually by the person who had just undertaken extraction of the support molded on the previous cycle, that person must first deposit the finished support before being able to grab hold of a reinforcing belt and position it inside the mold, this again constituting a nonproductive machine time. On the other hand, the generally high temperature of the molds also complicates these operations.
Owing to the duration and variability of that immobilization time and, therefore, of opening of the mold, temperature regulation of the different parts of the mold is rendered complex. In fact, if that duration is variable, the natural cooling of the walls of the mold also becomes variable.
One objective of the invention is to make it possible to reduce the average duration of a manufacturing cycle in relation to the known method. Another objective of the invention is to reduce the dependence of the process on availability of labor, particularly in order to render performance of the manufacturing equipment more efficient and more consistent, which also results in greater uniformity of production and, therefore, potentially better manufactured quality control. A further objective of the invention is to make press loading and unloading operations possible without having to extract the mold or a portion of same from the press. Another objective of the invention is the most compact possible means of using ordinary presses and not those specifically dimensioned for that application. A further objective of the invention is a method and device making possible substantial if not total automation of production.
The method and device of the invention make it possible to attain these different objectives and others which will appear on the description of preferred embodiments.
The invention consists of a method of manufacture of a support intended to be mounted on a tire rim of a vehicle, said support having an axis A, a base limited by a roughly cylindrical radially inner face intended to be mounted on said rim, a crown intended to bear the load and a body joining said base to said crown, said base comprising a substantially inextensible circumferential reinforcement, said body containing a plurality of roughly axial recesses coming out of said support on at least one side, said manufacturing process using a mold of axis corresponding to said axis A and the said mold comprising:
an inner core for molding said radially inner face,
a crown molding ring, said ring comprising at least two component parts radially mobile relative to each other, the said component parts making it possible to mold a radially outer face of said crown,
at least one shell bearing a plurality of axial fingers for laterally molding said body and said recesses,
said core, said ring and said shell cooperating in order to define, at least in part, a closed molding cavity for molding said support, the said core, comprising at least two component parts and being capable of taking a molding configuration in which said component parts form a circumferentially continuous molding surface for molding said radially inner face, the molding surface being defined by a reference diameter xcfx86, corresponding to the inner diameter of said support, the said core also being capable of taking a mold stripping configuration, defined by an overall length E around said molding surface less than the product of the number xcfx80 and the reference diameter xcfx86, and said manufacturing process comprising the following stages:
establishing the mold stripping configuration of the core,
placing a belt containing the said circumferential reinforcement around said core,
establishing the molding configuration of said core,
closing the mold,
forcing an injectable material under pressure into said molds,
opening the mold,
establishing the mold stripping configuration of said core,
removing said molded support,
the said process being characterized in that, on a given manufacturing cycle, the said belt is introduced in a volume described by the opening motion of said mold before a support molded on a previous manufacturing cycle is removed from said mold.
The method of the invention is, furthermore, preferably characterized in that, in a given manufacturing cycle, said belt is placed around said core before a support molded on a previous manufacturing cycle is removed from said mold.
The method of the invention is, furthermore, preferably characterized in that, the said axis of said mold being roughly vertical, said core, said shell and said ring having relative motions along said ax is on opening of the mold, said molded support is maintained, after its molding, after opening of the mold and before its removal, in contact with at least one wall of said molding cavity and in a vertically higher position than a mid-plane of said volume described by said opening motion.
The method of the invention is, furthermore, preferably characterized in that, said belt being introduced by means of a handling tool, the support molded on said previous cycle is removed by means of said handling tool.
The method of the invention is, furthermore, preferably characterized in that the stage of introduction of said belt and the stage of removal of said molded support are carried out by a roughly horizontal displacement of said handling tool.
The invention also relates to a device for the manufacture of a support designed to be mounted on a vehicle tire rim, said support having an axis A, a base limited by a roughly cylindrical radially inner face intended to be mounted around said rim, a crown intended to bear the load and a body joining said base to said crown, said base comprising a substantially inextensible circumferential reinforcement, the body containing a plurality of roughly axial recesses coming out of said support on at least one side, said device comprising a mold of axis matching said axis A and the said mold comprising:
an inner core for molding said radially inner face,
a crown molding ring, said ring comprising at least two component parts radially mobile relative to each other, the said component parts making it possible to mold a radially outer face of said crown,
at least one shell having a plurality of axial fingers for laterally molding said body and said recesses,
said core, said ring and said shell cooperating in order to define, at least in part, a closed molding cavity for molding said support, the said core comprising at least two component parts and being capable of taking a molding configuration in which said component parts form a circumferentially continuous molding surface for molding said radially inner face, the molding surface being defined by a reference diameter xcfx86 roughly corresponding to the inner diameter of said support, the said core also being capable of taking a mold stripping configuration, defined by an overall length E around said molding surface less than the product of the number xcfx80 and the reference diameter xcfx86, the said device being characterized in that each of the elements of an assembly consisting of said ring, said shell and said core is axially mobile relative to the other elements of said assembly.
The device of the invention is, furthermore, preferably characterized in that the said axis of said mold is roughly vertical.
The device of the invention is, furthermore, preferably characterized in that, at least a part of said mold being roughly stationary, other parts of said mold being movable along the axis of the mold, said device makes possible a movement of said moving parts directed downward in order to open the mold.
The device of the invention is, furthermore, preferably characterized in that, said mold comprising two shells capable of laterally molding the respectively opposite axial faces of said body, said shells bearing fingers capable of molding the said recesses, the said fingers of a shell capable of molding a face of said body are circumferentially interposed between the said fingers of a shell capable of molding the opposite face.
The device of the invention is, furthermore, preferably characterized in that it comprises a handling tool capable of being displaced in a roughly horizontal plane, said handling tool being capable of introducing said circumferential reinforcing belt and of removing said molded support.
The device of the invention is, furthermore, preferably characterized in that, the handling tool having a plurality of roughly vertical and radially mobile contact surfaces, the said handling tool is capable of radially maintaining said belt in a roughly cylindrical configuration, capable of positioning said belt in the axis of the mold and capable of receiving said molded support.
The device of the invention is, furthermore, preferably characterized in that, the handling tool having means of radial retention of said belt against said contact surfaces, said means are source of low pressure placed within said contact surfaces.
The device of the invention is, furthermore, preferably characterized in that, said handling tool having a generally horizontal upper face capable of bearing said molded support, said molded support is, on its removal, maintained relative to said handling tool by forces of gravity.
The method of the invention can be applied to the manufacture of supports from any injectable material, that is, capable of being introduced under pressure into the cavity of a mold. Such a material can consist of a reticular rubber compound or a thermoplastic polymer-base or thermosetting polymer-base compound, such as a thermosetting polyurethane.
A compound with base of at least one diene elastomer is preferably used as reticular rubber compound. A diene elastomer is understood, as known, to be an elastomer originating at least in part (i.e., a homopolymer or a copolymer) from diene monomers (monomers carrying two carbonxe2x80x94carbon double bonds, conjugated or not).
After entrance into the mold, the injectable material acquires the final mechanical characteristics necessary for operation. In the case of an elastomer or thermosetting material, that modification will be occasioned by a reticulation. With a thermoplastic material, the final mechanical characteristics are obtained by cooling.
In the description which follows, the case of manufacture of a support consisting of a reticular rubber compound is mainly illustrated. The description and drawings are directed to preferred embodiments of the invention.